The invention relates generally to an apparatus and method for performing a cardiovascular surgical technique and, more specifically, to an apparatus and method for the significantly less invasive repair of an infra-renal abdominal aortic aneurysm.
Recent statistics state that some 20,000 patients per year are admitted to a hospital only for the treatment of an aortic aneurysm. Another 76,000 patients per year have the treatment of an aortic aneurysm listed as one of the reasons for admission. The pain and danger to life usually associated with aortic aneurysms require some form of surgical treatment in a majority of cases. Generally accepted forms of treatment cause significant trauma to the patient. The two most widely used treatments are resection of the aneurysm or the implementation of an axillobifemoral bypass accompanied by a clotting of the aneurysm. The resection method requires a large incision into the abdominal cavity with surgical insertion of a prosthetic graft inside the damaged section. The surgical invasion of the abdominal cavity greatly increases the complications and mortality which result from the procedure, especially with respect to the majority of those patients with such aneurysms that also exhibit other reasons for hospitalization.
The axillobifemoral bypass method leaves the aneurysm open at the proximal end. The clot of an infra-renal aneurysm may propagate over the renal arteries causing loss of blood flow to the kidneys and possibly resulting in renal failure. Additionally, the grafted artery positioned during the method is very near the surface of the skin where it is susceptible to damage. The substantial rerouting effected by the bypass may also cause complications yet to be identified. Both current treatments are significantly invasive; not infrequently a patient dies during or as a result of the repair surgery.
A less invasive surgical method was recently proposed in U.S. Pat. No. 4,140,126 to Choudhury. The patent teaches a method for repairing an aortic aneurysm using a catheter inserted into the femoral artery and fed up to the site of the aneurysm. The only incision required is relatively small and is made in the leg of the patient. Fluoroscopic or X-ray techniques are used to position the catheter during the surgery. The catheter carries a pair of expanding rings spaced slightly more than the length of the aneurysm. A plurality of anchoring pins, which extend radially of the catheter, are attached to the rings. The prosthetic graft is held by the anchoring pins in a collapsed position smaller than the inside diameter of the artery. Once inserted, the rings are expanded and the anchoring pins penetrate the aortic walls, holding the graft in place with the help of the hemodynamic pressure of blood in the aorta.
The Choudhury method, while much less invasive than the generally accepted surgical techniques, has several distinct disadvantages. The anchoring pins used to hold the graft in place, first on the catheter and then in the aorta, pierce the aortic wall and may cause significant injury to the aorta, especially near the region of the aneurysm that has already severely weakened the aorta. The pins do not reliably hold the graft in position in contact with the walls of the aorta. The method also is carried out while blood continues to flow through the aorta, the aneurysm site, and the femoral artery. Additionally, the graft of Choudhury extends only a very small distance below the site of the aneurysm; the area of healthy vessel to which it must become attached is very small, with the consequence that leakage around the graft may occur or that the graft may not adhere to the vessel.